1. Field of the Invention
The present invention relates to an image display method, apparatus and program for implementing the method. More specifically, the present invention is directed to an image display method, apparatus and program for implementing the method, in which a plurality of different images is displayed on a screen for comparative observation based on a plurality of image data files, each representing each of the different images.
2. Description of the Related Art
Comparative image observations are performed by simply placing the images side by side for those recorded on recording media, such as papers or films. In addition, if the recording media are films, they may be placed in a viewing box (Schaukasten) arranged side by side for comparison.
For digital images, several different image display methods for use in the comparative observation are proposed, as described, for example, in Japanese Unexamined Patent Publication Nos. 8(1996)-076741 and 8(1996)-186762. In the methods, images under comparative observation are displayed on the same screen of a display device, such as a CRT, LCD or the like, or each of the images is displayed on the respective screens of a plurality of different display devices arranged side by side.
Another type of image display method is also proposed as described, for example, in Japanese Unexamined Patent Publication No. 2002-158923. In the method, an image subtraction process (subtractive operation) is performed between the images to be used for comparative observation to generate a differential image that indicates the difference between the images, which is then used for observing the extracted difference.
The image display method that displays a plurality of images on the same screen, however, has the disadvantage that each of the images displayed on the screen is too small for accurate observation. On the other hand, the image display method in which respective images are displayed on the respective screens of a plurality of different display devices has the disadvantage that the entire display system becomes sizable, resulting in limited locations for installation and increased costs. In addition, both methods have another disadvantage in common that images are placed apart from each other in no small extent, so that the observer has to look at these images by shifting the visual axes, which is burdensome and exhausting for the observer.
The method using a differential image to observe the difference between the images has the disadvantage that the comparative image observation may sometimes become difficult simply because the differential image is a different image from either of the original images, making it difficult for the observer to correctly identify the subject of the image.
One promising idea which might be conceivable for avoiding these problems is a switch display method in which each of the images under comparative observation is switch and display on the screen of a single display device. Simple switching of the images, however, may result in faded memory of the previously displayed image if the switching time is relatively long, or it may result in double images to be observed which are superimposed on top of another due to the afterimage effect if the switching time is relatively short. Thus, the method also suffers from the problem that effective and stable comparative image observation is not provided with this method.